Water treatment



April 4, 1967 R, C, ULMER ET AL WATER TREATMENT 5 Sheets-Sheet l FiledJune l, 1964 NNY INVENTORS RICHARD C. UL-MER Jol-1N J- KURPEN EYW MATTORNEY pri 4, 1967 R C, ULMER ET AL WATER TREATMENT 5 Sheets-Sheet 5Filed June l, 1964 vom M W WANG? Sbxnw INVENTORS R ICHAR D C. .JOHN JULM ER KLJFQPEN EY ATTORN EY United States Patent Oiifice 3,312,6lPatented Apr. fl, 1967 3,312,616 WATER TREATMENT Richard C. Ulmer,Simsbnry, and John J. Kurpen, Thompsonviile, Conn., assignors toCombustion Engineering, Inc., Windsor, Conn., a corporation of DelawareFiled .lune l, 1964, Ser. No. 371,344 8 Claims. (Cl. 21d-26) The presentinvention relates to the treatment of water for the removal of bothdissolved solids and dissolved oxygen and more particularly to the useof treated lion exchange materials for the removal of `both solids andoxygen particularly during start-up of a -boiler when conventionaldeaerators may be inoperative.

In the operation of boilers, it is desirable and often necessary toremove not only the dissolved solids from the water but also to removethe dissolved oxygen. Such materials in boiler water can cause seriouscorrosion and deposit problems. Most modern steam generating plants andparticularly those having once-through boilers utilize deimineralizingequipment to remove the dissolved solids Vand steam deaerators to removethe dissolved oxygen. Oxygen |becomes less soluible as the Watertemperature is increased so that it is easily removed 'by bringing theWater to a boil. In a steam! deaerator the water is :broken up into aspray or lm and then swept with steam to force out dissolved gases suchas oxygen and carbon dioxide. Since steam is available during Iboileroperation, such a method of oxygen removal is practical and economical.However, during start-np of thebo-iler, steam is not available from theboiler itself for deaerator operation. Therefore, unless an auxiliarysteam supply is provided, the deaerator will not function. Provision ofan auxiliary steam supply would in many cases be very costly. It is thisproblem to which the present invention is directed.

An object of the present invention is, therefore, to p-rovide a systemfrom the removal of iboth dissolved solids `and gases from water.

It is a further object to provide a system for oxygen removal whenconventional deaeration equipment is inoperative.

A .particular object of the invention is to utilize the already existingdemineralizing system yfor bot-h oxygen and solids removal.

Other objects and the attendant advantages will become apparent from thedescription of the invention which follows.

rThe present invention is primarily directed to the removal of thedissolved oxygen lfrom the water during start-up When steam is notavailable by activating the already available ion exchange materialslfor oxygen removal as well as for solids removal.

Systems have been employed in the past wherein ion exchange resins aretreated so that they will remove oxygen from water. One such system isdescribed in an article by Mills and Dickinson in the December i949,-issue of Industrial and Engineering Chemistry on page 2842 entitledOxygen Removal From Water by Amine Exchange Resins. In such a system theresin is treated with cupric sulphate and then With sodium hy'drosulteto reduce the cupric ion to metallic copper. The copper then is oxidizedby the dissolved oxygen in the Water and the dissolved oxygen :therebyremoved from the Water. However, resins treated in this manner do notretain their ion exchange capacity and thus remove only the oxygen fromthe Water While leaving the solids.

Another system for oxygen removal and the one forming the basis tor thepresent invention is described in an article 'by Potter and Whiteheadentitled Continuous Removal of Dissolved Oxygen by Established IonExchangers, appearing in the Nov. 7, 1957, issue of Journal of AppliedChemistry. In this oxygen removal system the resin supports an insolubledeoxygenating substance precipitate within the pores of the resinmatrix. Suitable substances to precipitate in the resin are ferrous ormanganous hydroxide each of which reacts extremely rapidly With thedissloved oxygen in water. The resin, whether cationic or anionic,retains its capacity for ion exchange.

Considering first the conversion of a strongly lacidic cationic resininto the deoxygenating state, a conventional resin such as Zeo-Kanb 225(trade name of Permutit Co., Ltd., England) is treated with strongferrous (or manganous) sulfate solution which converts the resin fromits initial hydrogen -or sodium form to the ferrous (or manganous) form.The resin in this latter form is then activated Lwith a solution of asoluble alkali such as sodium hydroxide. The resin itself is therebyconverted to the alkali for-m and ferrous (or manganous) hydroxide isprecipitated Within the resin. If sodium hydroxide has been used theactivated resin will be in the sodium -form `and in such a state can beutilized to both deoxygenate and soften Water in a single continuousprocess. However, the cations lcannot be totally removed from the Watersince the resin is not in the hydrogen form.

An anionic resin may be converted to the deoxygenating form by treatingthe hydroxyl form of the resin with a strong ferrous (or manganous)sulfate solution which will convert the resin to the sulfate rform withferrous (or man-ganous) hydroxide precipitated Within the resin pores.Such a resin will deoxygenate water and exchange the sulfate for `anionsin the Water but since the resin is in the sulfate form the anionscannot be totally removed. Deoxygenating resins such as those formed bythe process as outlined in the Potter and Whitehead article are utilizedin a novel manner in the present invention.

Since oxygen removal Kby the use orf steam operated deaerators is aneconomical method of operation, the present invention does not suggestthe ycomplete substitution of such equipment but rather the provision ofauxiliary oxygen removal means for use only when the deaerator isinoperative. The present invention therefore utilizes the existing ionexchange apparatus modiled to facilitate oxygen removal in conjunction'With the steam operated deaerator. The ion exchange materials areregenerated and activated for oxygen removal lfor use during start-upand then after the steam deaerator becomes operative, the exchangematerials yare utilized `for demineralization as usual. Such a systemand method of operation provides oxygen removal during start-up with aminimum capital expenditure.

The teachings of Potter and Whitehead in the abovementioned article areextended and modified by the present invention so that ion `exchangeresins can be effectively used to remove both solids and dissolvedoxygen simultaneously. The cation and anion resins mentioned in thearticle are left in the sodium and sulfate form, respectively, andtherefore the resins cannot 'be utilized for demineralization. The anionresin can be treated with sodium hydroxide after activation With ferroussulfate to convert the lresin back to the hydroxyl form thus permittingthe ani-on resin to remove anions from the Water as well as removeoxygen. The present invention also combines a novel scheme forconverting the cation resin to the hydrogen form as well as the anionresin to the hydroxyl form so that -both resins Will demineralize asWell as deoxygenate.

The cation resin of Potter and Whitehead is in the- It cannot beconverted.

sodium form after activation. to the hydrogen form 'by the use ofconventional acids since such acids would react with the precipitatedhydroxide in the `resin pores. However, the sieve action olf the ionexchange resins can be utilized to advantage in this regard. lf highmolecular 'weight aoids which have large size anions are employed toconvert the cation resin to the hydrogen form, the large anions will notenter the resin pores and thu-s they will not be available to react withthe precipitated hydroxide. Examples of such acids are ligninsulphonicacids and pectic Iacid. The ligninsulphonic acid is obtained by ionexchange techniques from waste sulphite pulping liquor while the pecticacid is produced from pectin which lis derived from fruit rinds. Theligninsulphonate anion, for instance, is too large to enter the pores ofthe resin and 'react there- -with while the hydrogen ion 'is availablet-o exchange with the sodium ion on the cation resin. After treatmentwith suc-h acids, the cation resin will be in condition to remove bothoxygen and cations from the incoming water.

Another favorable aspect of the use of acid with extremely large anionsis that they may be utilized to convert the cation resin in the mannerdescribed above in a mixed bed exchange unit without separating theanion and cation resins without materially effecting the anion resin.The ligninsulphonate anion, 'for instance, will exchange very slowlywith the anion resin and the practical effect will fbe that nosignificant exchange takes place. Therefore, ligninsulphonic or pecticlacid or some similar largemolecular weight acid can be added to -amixed bed of cation and Ianion exchange resins to convert the cationresin to the hydrogen Lform without affectin-g the anion resin therebyleaving itin the hydroxyl form. Also, the acid will not effect theprecipitated Ihydroxide in either resin since the anion of the acid istoo large to enter the pores of the resin matrix and thus cannot reachthe hydroxide. For a better understanding of this invention referencemay `be had tothe accompanying drawings wherein:

FIG. l schematically illustrates a vapor generating cycle in which thepresent invention will be employed;

FIG. 2 illustrates a mixed bed demineralizing system incorporating thepresent invention; and

FIG. 3 schematically illustrates an alternative arrangement for thedemineralizing-deoxygenating system.

FIG. 1 shows a vapor generating system including a Vapor generator whichsupplies steam to turbines 12 and 14. Between the turbines 12 and 14 isa reheater 16 which serves to raise the steam temperature and pres- Sureto the desired values Afor use in the second turbine 14. The steam afterpassage through turbine 14 is condensed in condenser 18 and recirculatedthrough the system by condensate pump 20. Make-up water from supplymeans 22 is introduced into the system to replinish. any losses whichhave occurred. From the condensate pump the water flows through ademineralization system 24, a low pressure feedwated heater 26 and thento the deaerator 28. The deaerator as previously discussed requiredsteam for its operation. As shown in FIG. l this steam may be derivedfrom any one of several locations via line 29 depending upon thetemperature and pressure of the steam desired and the conditionsexisting at the various locations. The dea'erated water then passesthrough feed pump 30 and high pressure feedwater heater 32 back to thevapor generator 10. It can be seen that during start-up, steam from theVapor generator will no ybe available to operate the deaerator 28. Thepresent invention overcomes this problem by the use of a specialdemineralizing system 24, alternative arrangements of which areillustrated in detail in FIG. 2 or 3.

The system illustrated in FIG. 2 utilizes two mixed bed ion exchangeunits 34 and 36 which are connected in parallel with each other relativeto the feedwater inlet 38 and the water outlet 40. During normaldemineralization one of these units would be in a service cycle whilethe other unit is either on a stand-by basis or under-V goingregeneration. In the system illustrated the exchange unit 34 is employedonly for demineralization while unit 36 is employed both fordemineralization and deoxygenation.

'The units 34 and 36 are conventional mixed bed units identical inconstruction and therefore only the internal construction of unit 34 hasbeen illustrated. The feedwater enters the unit through valve 42 and isdistrubuted by the Ycollector and distributor means 44.- The water flowsdownwardly thro-ugh the column and the treated water is extractedthrough valve 46. When it is desired to regenerate the unit 34 the unitis backwashed with water introduced through valve 48 and extractedthrough valve 50. This backwash will separate the resins into twodistinct layers since the lighter anion resin will rise to the top andlthe heavier cation resin will settle to the bottom. Sulfuric acid isthen introduced from supply tank 52 through valve 54 and extracted fromvalve 56 so that the acid will flow only through the cation resininasmuch as the interface of the resins is located at the interfacecollector 58. The anion resin is then regenerated with sodium hydroxidefrom supply tank 60 introduced through distributor 62 via valve `64 andwithdrawn from the column through interface collector 58 and valve 56.In order to prevent sodium hydroxide diffusion into the cation resin,one of two techniques is employed. Either the cation and anion resinsare regenerated at the same time or water is introduced into the bottomof the column and withdrawn through the'interface collector during anionregeneration. Either of these procedures will provide the upward ow inthe cation resin necessary lto prevent sodium hydroxide from flowingdown through the lower portion of column. The resins are then rinsedwith water introduced through valves 8 and 66 and withdrawn throughvalve 56. After rinsing, the cation and anion resins are mixed by theagitating effect of air forced in through valve 63 by blower 70. Thecolumn is then ready for another service cycle.

The construction of column 36 is identical to that of column 34 andduring normal demineralization it would be operated alternately withcolumn 34 and regenerated in a similar maner. However, column 36 hasbeen provided with additional connections to facilitate activation ofthe resin therein for oxygen removal.

Assuming that the cation and anion resins in column 36 are initially inthe hydrogen and hydroxyl form, the method of activating the column foroxygen removal is as follows. Ferrous sulfate is added to the columnfrom supply tank 72 through the distributor in column 36 correspondingto the distributor 62 in column 34. The ferrous sulfate flows downwardlythrough the mixed resins converting the cation resin to the ferrous formand the anion resin to the sulfate form. Ferrous hydroxide will beprecipitated within the pores of the anion resin. The reactions in eachresin are as follows.

convert the anion resin to the hydroxyl form. The reactions involved inthis step are as follows.

To convert the cation resin from the sodium form to the hydrogen form,ligninsulphonic acid, which will be designated' as I SOaH, is introducedinto the column from supply tank 74. This high molecular weight acidwill convert the cation resin to the hydrogen form according to thefollowing reaction.

As previously stated the high molecular weight anion portion of the acidwill be exchanged with the anion resin in an insignificant amountthereby leaving the anion resin in the hydroxyl form. At this stage bothresins have ferrous hydroxide precipitated Within their pores and thusthey are ready for both demin'eraliZation and oxygen removal. Thereactions involved in the service cycle for each of the resins withWater containing calcium and chlorine ions plus dissolved oxygen are asfollows.

(6) Cation resin:

Upon exhaustion of the resins sulphuric acid is passed downwardlythrough the column to remove the ferrie hydroxide from each of theresins and to convert the cation resin to the hydrogen form. Thereactions involved in this step are as follows.

(8) Cation resin:

At this stage the resins may be separated by the use of a backwash aswas described in conjunction with the regeneration of column 34. Thisseparation is for the purpose of isolating the anion resin so that itmay be converted fromthe sulfate form to the hydroxyl form by owingsodium hydroxide downwardly through the top anion resin layer whilepassing water upwardly through the cation resin. The cation and anionresins are now in the hydrogen and hydroxyl forms, respectively, andthus ready for demineralization service or for reactivation for oxygenremoval as desired.

Instead of separating the resins prior to this latter treatment withsodium hydroxide, the mixed resins may be treated with sodium hydroxidewhilch will convert the cation resin to the sodium form as well asconvert the anion resin to the hydroxyl form. Thereafter, the cationresin may be converted back to the hydrogen form with ligninsulphonicacid without separating the resins.

Provisions for activation of the resins for oxygen removal has only been,illustrated for column 36 of FIG. 2. It is obvious, however, thatsimilar provisions could be made for column 34 so that the columns couldbe alternately used for oxygen removal as well as for demineralization.

The arrangement shown in FIG. 3 applies the principles of the presentinvention to conventional 2step demineralizers wherein each columncontains only a cation or anion resin whereas the arrangement shown inFIG. 2 employed a mixed bed column. Although various arrangements of theseparate bed system are possible, the arrangement of FIG. 3 employs onepair of ion exchange units for oxygen removal while the other pair isemployed to demineralize the deoxygenated water. Columns 76 and 7S arecation and anion columns, respectively, and each is provided withoxygenremoval activating systems. These two columns 76 and 78 when notutilized for oxygen removal are employed alternately with columns 8d and82 for demineralization. When column 76 is activated for oxygen removalthe resin therein is in the sodium form and thus will not remove cationsfrom the incoming water. Likewise, the resin in column 78 is in thesulfate form and will not remove anions from the water. Therefore, thewater leaving column 78 is fed via line 84 to columns 80 and 82 whereinthe water is demineralized in a conventional manner. An alternative tothis arrangement would be to convert the resin in column 76 to thehydrogen form with ligninsulphonic acid and to convert the resin incolumn 78 to the hydroxyl form with further sodium hydroxide treatmentin which case the water would be both deoxygenated and demineralizedafter passing through the units 76 and 78. The water could then be feddirectly to the boiler without passing through columns S0 and 82.

The operation of the demineralizing-deoxygenating systems described whenused in conjunction with the deaer-ator in a vapor generating circuit isas set forth below. Prior to start-up of the furnace the demineralizingsystem is activated for oxygen removal. This accomplished by the methodspreviously described such that column 36 or columns 76 and 78, dependingupon the particular system employed, are activated for oxygen removal.Upon startup the feedwater is routed through the activated column orcolumns and then fed through the low pressure feedwater heater 26. Thewater may then either pass through the inactive deaerator to the feedpump or bypass the deaerator through the valved line 86. The valveswhich control the steam ilow to line 29 are all closed during thisinitial stage of operation. As steam becomes available, at point 38 forinstance, and as the Aoxygen removal power of the activated resin isdepleted, steam is admitted to the deaerator andthe feedwater is routedtherethrough. The deaerator is now serving to deoxygenate the feedwaterand this Vfunction of the demineralizing system is no longer needed.

Therefore, the feedwater is re-'routed from the activated column orcolumns to the other columns, for conventional demineralizing treatment.The columns which were activated for oxygen removal are treated in themanner previously described to remove the spent deoxygenating materialsfrom the resin and to prepare the resin for subsequent use as analternate or standby demineralizer.

1t can be seen that such a system involves very little capitalexpenditure as compared with the cost of providing an auxiliary steamsource. All that is necessary in the system of the present inventionover and above that normally required for a demineralizing system is thesupply tanks for the additional activating materials and the additionalpiping and valves associated therewith.

While several embodiments of the invention have been shown and describedit will be understood that such showings are illustrative rather thanrestrictive and that changes in construction and arrangement of partsand in the steps involved may be made without departing from the spiritand scope of the invention yas claimed.

We claim:

1. The method of operating an ion exchange unit containing cationexchange material comprising the steps of treating said material with ametallic salt to convert said material to a metallic form, treating saidmetallic form of thev material with alkali to precipitate metallichydroxide within the pores of the material, treating the resultingmaterial with a high molecular weigh acid, the anion portion of saidacid being of such Ia size that it will not enter the pores of saidresulting material and therefore will not react with said metallichydroxide, said acid converting said resulting material to the hydrogenform and thereafter passing water in contact with said hydrogen form ofthe said resulting material to remove cations and oxygen from saidwater.

2. The method of claim 1 wherein said metallic salt iS selected from thegroup consisting of ferrous and manganous sulfate and said highmolecular weight acid is selected from the group consisting ofligninsulphonic acid and pectic acid.

3. The method of operating a mixed bed ion exchange unit containingcation and anion exchange material comprising the steps of treating saidmateri-al with a metallic salt to convert said cation exchange materialto the metallic form and to convert said anion exchange material to thesalt form and to precipitate metallic hydroxide within the pores of saidconverted anion exchange material, treating said converted material witha hydroxide to precipitate metallic hydroxide within the pores of saidconverted cation mate-rial and to reconvert said converted anionmaterial from said salt form to the hydroxyl form, treating theresulting material with an acid to reconvert said converted cationexchange material to the hydrogen form, said acid having a highmolecular weight such that the anion portion thereof is of such size soas to be unable to enter the pores in said resulting material and unableto react with said precipitated metallic hydroxide, and thereafterpassing water in contact with the thus treated material to remove oxygenand ions therefrom.

e. The method of claim 3 wherein said acid is selected from the groupconsisting of ligninsulphonic acid and pectic acid and said metallicsalt is selected from the group consisting of ferrous manganous sulfate.

5. The method of feedwater treatment for a steam generating systemwherein said system includes a steam generator, a steam operateddeaerator, Iand an ion exchange system containing ion exchange materialcomprising the steps of activating at least a portion of said ionexchange material for the removal of dissolved gases from said feed-Water and placing at least a portion of said ion exchange material inthe hydrogen form for cation removal, passing eedwater in contact withsaid activated portion and said portion in the hydrogen form Ito removeboth cations and dissolved gases from said feedwater when steam isunavailable for said steam operated deaerator, treating saidfeedwater insaid deaerator for the removal of dissolved gases when steam isavailable and thereafter treating said feedwater in said ion exchangesystem for the removal of ions.

6. The method of claim 5 wherein said activated portion and said portionin the hydrogen form are the same and wherein said portionssimultaneously remove ions and dissolved gases.

7. A feedwater system for a steam generating unit comprising incombination, a steam operated deaerator, means for supplying steam tosaid deaerator from said steam generating unit, an ion exchange system,means for feedexchange material to the hydrogen form without reactingsignificantly with said precipitated metallic hydroxide whereby saidprecipitatedmetallic hydroxide will be available for removing oxygenfrom said water and whereby said treated cation exchange material in thehydrogen form will be available for removing Acations from said water.

8. A feedwater system for a steam generating unit comprising incombination, a steam operated deaerator, means for supplying steam tosaid deaerator from said generating unit, an ion exchange system, meansfor feeding Water to said steam generating unit through said ion eX-change system and said deaerator, said ion exchange system includingcation exchange material, means for activating said material forthe-removal of dissolved gases from said feedwater, means for convertingsaid material to the hydrogen form while it is still activated for gasremoval whereby said material may simultaneously remove gases andcations from said water when steam is not available for said steamoperated deaerator.

References Cited by the Examiner UNITED STATES PATENTS 2,710,255 6/1955Van Blaricom etal. 210-34 3,183,184 5/1965 Fisher 210-26 3,183,1855/1965 Haagen 210-26 3,210,912 10/1965 Peake et al. 55-39 OTHERREFERENCES Betz Handbook of Industrial Water Conditioning, BetzLaboratories, Inc., Philadelphia, Pa., copyright 1957, pages 26 and 52relied upon.

MORRIS O. WOLK, Primary Examiner.

E. G. WHiTBY, Assistant Examiner.

1. THE METHOD OF OPERATING AN ION EXCHANGE UNIT CONTAINING CATIONEXCHANGE MATERIAL COMPRISING THE STEPS OF TREATING SAID MATERIAL WITH AMETALLIC SALT TO CONVERT SAID MATERIAL TO A METALLIC FROM, TREATING SAIDMETALLIC FORM OF THE MATERIAL WITH ALKALI TO PRECIPITATE METALLICHYDROXIDE WITHIN THE PORES OF THE MATERIAL, TREATING THE RESULTINGMATERIAL WITH A HIGH MOLECULAR WEIGH ACID, THE ANION PORTION OF SIADACID BEING OF SUCH A SIZE THAT IT WILL NOT ENTER THE PORES OF SAIDRESULTING MATERIAL AND THEREFORE WILL NOT